Nikkei Electronics Asia reports on a Kapton Polymide ribbon capillary CPU liquid cooling system by Soliton R&D Corp of Japan. ; "A new type of water-cooling technology has appeared to handle IC heating issues in PCs and other equipment. Compared to existing water-cooling modules it seems to offer better heat radiation performance, smaller and lighter specs, and cheaper manufacturing. The new technology is under development by Soliton R&D Corp of Japan, a technology start-up involved in R&D of flexible circuit boards. The basic approach is to form an extremely fine network of channels through Cu foil, passing the water or other cooling medium. Eventually the firm hopes to form it as an integral part of the printed circuit board (PCB) or flexible circuit.
The firm commented that the prototype is already capable of cooling the surface temperature of a 150W IC low enough for normal operation. One of the reasons that Soliton's design achieves such high cooling performance is that it uses fine pipes - or capillaries. The total surface area can be maximized in comparison to the coolant volume, boosting performance. For example, the A4-size Cu sheet used as the radiator has a large number of capillaries running parallel, with a length of over 3 meters each for a total path length of 30 meters. The capillaries are 1.5mm in width, and 150µm deep. Both dimensions were based on the performance of the existing pump, and will be reduced to about 50µm square in future designs. These numbers are on a par with the "microchannel" design under development by Intel and others for microprocessor cooling.
A smaller capillary cross-section means that the Cu sheet can be made thinner, which is the key to smaller and lighter modules. The Cu sheet used in the prototype was 0.4mm thick, but Soliton expects to be able to reduce this to 70µm. At 0.4mm, the A4-size Cu sheet weighs over 200g, but this would be reduced to under 40g if only 70µm thick."